Variable valve activation mechanisms for internal combustion engines are well known. It is known to lower the lift, or even to provide no lift at all, of one or more valves of a multiple-cylinder engine during periods of light engine load. Such deactivation can substantially improve fuel efficiency.
Various approaches have been disclosed for changing the lift of valves in a running engine. One known approach is to provide a deactivation mechanism within the hydraulic lash adjuster (HLA) upon which a cam follower rocker arm pivots. Such an arrangement is advantageous in that it can provide variable lift from a single cam lobe by making the HLA either competent or incompetent to transfer the motion of the cam eccentric to the valve stem. A shortcoming of providing deactivation directly by the HLA is that because the cam lobe actuates the rocker near its longitudinal center point, the variation in lift produced at the valve-actuating end can be only about one-half of the extent of travel of the HLA deactivation mechanism.
Another known approach is to provide a deactivation mechanism in the roller finger follower itself, such as that disclosed in U.S. Pat. No. 6,604,498. In the mechanism disclosed, a two-part roller axle serves to selectively latch and delatch the roller from the body of the follower. The actuating mechanism needed to operate the deactivation mechanism resides adjacent one side of the roller finger follower body to act against an end of the two-part roller axle. For that reason, the mechanism occupies a substantial amount of space and can be cumbersome.
What is needed is a compact valve activation mechanism contained within a roller finger follower that is capable of deactivating an associated valve resulting in zero lift of the associated valve.